Fluoropolymer membranes such as PTFE membranes have several attractive properties, for example, compatibility with solvents and corrosive chemicals, ability to withstand high (e.g., sterilizing) temperatures, low pressure drop, toughness, insulating properties, non-adhesiveness, and resistance to damage, and, therefore, have found wide use in industry, for example, as a filtration medium for corrosive gases and liquids and as a separator in electrolytic cells and batteries. Although fluoropolymer membranes have these and other attractive properties, the industry has a desire to improve one or more of its properties. For example, there is a desire to improve the permeability, i.e., flow rate of fluids through the membranes.
Attempts have been made to produce highly permeable fluoropolymer membranes. Many of these attempts are based on stretching, with or without heat, to a large draw ratio, a pre-formed membrane such as a sintered fluoropolymer membrane. However, these attempts involve processes which are relatively complex, cumbersome, and/or expensive to practice; and these processes also alter (undesirably) other properties, e.g., porosity, of the membrane.
Thus, there exists a need for highly permeable porous fluoropolymer membranes. There further exists a need for thin porous fluoropolymer membranes having a desired porosity and/or pore rating. There also exists a need for a process for producing such porous fluoropolymer membranes.
The present invention provides for ameliorating at least some of the disadvantages of the prior art fluoropolymer membranes. These and other advantages of the present invention will be apparent from the description as set forth below.